I had forgotten about the blood types from the Eucharistic miracles. It would have been IMPOSSIBLE for medieval hoaxers to have done this. Blood groups were totally unknown until 1900 and the AB types are very rare to begin with.
As I said last night, people trying to pull of a hoax in the Middle Ages would only have been trying to fool their contemporaries and in the Middle Ages ALL BLOOD LOOKED THE SAME.
Well said.